LDAP over SSL connectivity

Hi all,

I am trying to connect to AD using LADP over SSL. I have following code, but I am getting exception (The LDAP server is unavailable). I can able to connect using LDAP test application on both 636 and 389 ports. I can able to connect using389 port but not from 636 port from below code.

Please suggest me if I am doing something wrong in my code.

Dim ldapErrorInvalidCredentials As Integer = &H31

        Dim activeDirectoryServer As String = "xyz.test.com:636"

        Dim activeDirectpryDomain As String = "test.com"

        Dim ldapConnection As LdapConnection = Nothing

        Dim user As String = "testUser"

        Dim ldapPort As String = "636"

        Dim Success As Boolean = False

        Try

            ldapConnection = New System.DirectoryServices.Protocols.LdapConnection(activeDirectoryServer)

            ldapConnection.SessionOptions.SecureSocketLayer = True

            ldapConnection.SessionOptions.ProtocolVersion = 3

            ldapConnection.AuthType = AuthType.Negotiate

            ' ldapConnection.SessionOptions.VerifyServerCertificate = New VerifyServerCertificateCallback(ldapConnection, cert)

            ldapConnection.AutoBind = False

            'ldapConnection.Credential = New NetworkCredential(username, password, activeDirectpryDomain)

            Dim cert As X509Certificate = New X509Certificate()

            cert.Import("C:\LDAP\cert.cer")

            ldapConnection.ClientCertificates.Add(cert)

            ldapConnection.Bind(New NetworkCredential(user , "testpassword", activeDirectpryDomain))

            Console.WriteLine(("Successfully authenticated to ldap server " & activeDirectoryServer))

        Catch ex As Exception

            Console.WriteLine("Failed")

        End Try